Stainless Steel Washer Size Chart — DIN 125, DIN 9021 & DIN 433 (M2–M64)
Three washer standards cover most metric bolted joints — DIN 125, DIN 9021 and DIN 433 — and each one gives a different outer diameter and thickness for the same bolt size. If you already know which standard you need, the individual product pages have the complete size run with tolerances. If you're trying to figure out which washer fits which application, or you just want to see how the three standards stack up against each other for a given M-size, this page puts them side by side.
How to read washer dimensions
Every flat washer drawing uses the same three figures, usually written d1 x d2 x s:
- d1 — bore (inside diameter). The clearance hole the bolt passes through. For a given bolt size, d1 is essentially the same across DIN 125, DIN 9021 and DIN 433 — it just needs to clear the bolt shank.
- d2 — outer diameter. This is where the standards diverge. DIN 125 is the general-purpose OD, DIN 9021 is a wide OD for load spreading, DIN 433 is a reduced OD for tight clearances.
- s — thickness. Also varies by standard; wider washers are usually thicker too, since they need more material to resist bending under clamp load.
All values below are in millimeters, nominal, for product grade A — the standard grade used for 304 and 316 stainless flat washers. That's the whole reason three standards exist for what looks like the same part: the bore stays put, and the OD and thickness change to suit the application.
Side-by-side comparison: DIN 125 vs DIN 9021 vs DIN 433
| Thread | Bore d1 | DIN 125 OD × thk |
DIN 9021 OD × thk |
DIN 433 OD × thk |
|---|---|---|---|---|
| M3 | 3.2 | 7 × 0.5 | 9 × 0.8 | 6 × 0.5 |
| M4 | 4.3 | 9 × 0.8 | 12 × 1.0 | 8 × 0.5 |
| M5 | 5.3 | 10 × 1.0 | 15 × 1.2 | 9 × 1.0 |
| M6 | 6.4 | 12 × 1.6 | 18 × 1.6 | 11 × 1.6 |
| M8 | 8.4 | 16 × 1.6 | 24 × 2.0 | 15 × 1.6 |
| M10 | 10.5 | 20 × 2.0 | 30 × 2.5 | 18 × 1.6 |
| M12 | 13 | 24 × 2.5 | 37 × 3.0 | 20 × 2.0 |
| M14 | 15 | 28 × 2.5 | 44 × 3.0 | 24 × 2.5 |
| M16 | 17 | 30 × 3.0 | 50 × 3.0 | 28 × 2.5 |
| M20 | 21 | 37 × 3.0 | 60 × 4.0 | 34 × 3.0 |
| M24 | 25 | 44 × 4.0 | 72 × 5.0 | 39 × 4.0 |
Look at M10 as an example: the bore is 10.5 mm regardless of standard, but DIN 125 puts 20 mm on the outside, DIN 9021 puts 30 mm, and DIN 433 only 18 mm. Same bolt, three different bearing areas.
Full size range: M2 up to M64
DIN 125 alone runs from M2 (small enough for instrument and electronics work) up through M36 and beyond in our production range, including in-between sizes such as M2.5, M18, M22, M27, M30 and M33 that aren't shown in the comparison table above. DIN 9021 and DIN 433 have their own size ranges, narrower at both ends than DIN 125. The comparison table above covers the sizes buyers ask for most — M3 to M24 — because that's where all three standards overlap and a side-by-side view is actually useful.
For the complete table on any one standard, including every intermediate size, exact tolerances and the largest sizes we produce, go to the dedicated page:
- DIN 125 flat washers — full size table →
- DIN 9021 fender washers — full size table →
- DIN 433 small-OD washers — full size table →
Which one do I need?
DIN 125 — standard OD, general use. This is the default flat washer for most bolted joints: general assembly, machinery, structural connections where the substrate is rigid and the hole is a normal clearance fit. If a drawing just says "flat washer" with no other qualifier, it usually means DIN 125.
DIN 9021 — large OD, load spreading. Outer diameter runs close to three times the bolt size. Reach for DIN 9021 when the material under the washer is soft or compressible (timber, plastic, thin sheet metal), when the clearance hole is oversized or slotted, or when the joint needs more bearing area to avoid pull-through under load. Also called a fender washer.
DIN 433 — small OD, tight clearance. Outer diameter is smaller than DIN 125. Use it where space around the bolt is limited — counterbored holes, cheese-head or cap screws, recessed fittings, or any assembly where a standard-OD washer would overhang or foul adjacent parts.
If you're working from an ISO or ASME callout instead of a DIN number, see DIN, ISO & ASME Washer Standards: Cross-Reference & Equivalents → for how the systems map to each other.
Tolerances and inch sizes — a note
The figures in the table above are nominal dimensions for product grade A, which is the tolerance class used for 304 and 316 stainless washers in DIN 125, DIN 9021 and DIN 433. Actual parts carry a tolerance band on bore, OD and thickness as defined in each standard — request the production drawing if you need the exact range for a specific size.
These are metric washers, sized by M-designation. Imperial (inch) washers are a separate system, ASME B18.21.1, covering SAE and USS series, sized by bolt inch fraction rather than millimeter. The two systems don't convert on a simple ratio, so we haven't included inch dimensions on this page — see the cross-reference guide for how metric and imperial washer standards line up.
What HUIHUI supplies
We produce DIN 125, DIN 9021 and DIN 433 washers in 304, 316 and 316L stainless, M2 through M64, as standard stock sizes or made to drawing for non-standard dimensions. Mill test certificates (EN 10204 3.1) available on request.
FAQ
What outer diameter does an M8 washer have?
It depends which standard. For an M8 bolt (8.4 mm bore) a DIN 125 washer is 16 mm OD x 1.6 mm thick, a DIN 9021 fender washer is 24 mm OD x 2.0 mm thick, and a DIN 433 small-OD washer is 15 mm OD x 1.6 mm thick. The bore is the same across all three — only the outer diameter and thickness change with the standard.
What is the size difference between DIN 125 and DIN 9021?
DIN 9021 has a much larger outer diameter than DIN 125 for the same bolt size — roughly 1.5 to 2 times wider, and often close to three times the nominal bolt diameter. For M10, DIN 125 is 20 mm OD while DIN 9021 is 30 mm OD. DIN 9021 is also thicker in most sizes. The bore diameter is identical between the two standards; only the bearing surface and thickness differ.
Do you supply M2 or very large washer sizes?
Yes. DIN 125 covers M2 up to M36 and larger in our production range, in 304 and 316 stainless. The side-by-side table on this page only lists the most commonly ordered sizes, M3 to M24. Full dimension tables including M2, M2.5, M18, M22, M27, M30, M33 and M36 are on the dedicated DIN 125, DIN 9021 and DIN 433 product pages, and we can produce beyond M36 to drawing on request.
How do metric washer sizes compare to inch (imperial) washers?
Metric washers (DIN 125, DIN 9021, DIN 433) are sized by M-designation and millimeter dimensions. Imperial washers follow a separate system, ASME B18.21.1, sized by bolt inch fraction under SAE or USS series, with dimensions in inches rather than millimeters. The two systems are not interchangeable by simple conversion — a washer has to be ordered against the correct standard for the bolt it will run on. See our DIN, ISO and ASME cross-reference guide for how the systems line up.
Are the dimensions in this chart exact or nominal?
The figures in this chart are nominal dimensions for product grade A, the standard tolerance class for DIN 125, DIN 9021 and DIN 433 washers. Actual production parts carry tolerances on bore, outer diameter and thickness as defined in each standard. For tolerance ranges on a specific size, request the production drawing or refer to the full table on the relevant product page.
Need a specific size or standard?
Send the standard, M-size, material grade (304 / 316 / 316L), and quantity. We reply with pricing and lead time within one business day.
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